1. Field of the Invention
This invention relates to a device for use in a furnace exhaust system for thermoelectric generation, and more particularly, to a device having thermoelectric modules mounted between a pair of temperature controlled members, the device can be mounted in the exhaust stream of a furnace, e.g. a furnace for melting glass-batch materials whereby the thermoelectric modules generate a voltage.
2. Discussion of the Presently Available Technology
Devices used for thermal generation of electricity can include one or more thermoelectric modules mounted between a pair of members. The thermoelectric modules respond to the temperature differential between the members by generating a voltage. The greater the temperature difference between the members, the greater the voltage and power generated.
In one arrangement, the device includes the thermoelectric modules between an outer member and an inner member with the outer member maintained at a lower temperature than the inner member. One such device is a Global Thermoelectric cylinder TEG (model 7120) having a hot face which is a cylinder having a 3.5 inch diameter and a cold face which is a cylinder of larger diameter having a water cooled jacket over the cold face. The outer member is at a lower temperature than the inner member to take advantage of the thermal expansion of the inner member to maintain surface contact between the thermoelectric modules and the members. More particularly and is appreciated by those skilled in the art, the thermoelectric modules to operate efficiently are maintained in surface contact with the outer surface of the inner member and the inner surface of the outer member. In most applications, the temperature difference between the members is the result of heating only one member. When the member heated is the inner member, the inner member expands moving toward the outer member and moving the thermoelectric modules toward the inner surface of the outer member. On the other hand, if the outer member is heated, the outer member expands moving away from the inner member and the thermoelectric modules.
In the instance when heated exhaust streams can be flowed through narrow passageways or openings, e.g. a passageway through the center portion of the inner member, the presently available technology is acceptable. However, where there is a large volume of exhaust gas, or there is low pressure/low flow of exhaust gas, and/or the exhaust gas has particles, the presently available thermoelectric generating devices have limitations. More particularly, the particles in the exhaust gas can accumulate in the passageway of the inner member and stop or reduce the flow of exhaust gas through the passageway. Reducing the flow of the exhaust gas through the exhaust system of the furnace to move the exhaust gas through the passageway of the inner member of the thermoelectric generating device can have an adverse effect on the process and/or furnace components. For example but not limiting to the discussion, altering or interrupting the flow of the exhaust stream through the exhaust system of a furnace for melting glass batch materials can result in over heating sections of the refractories of the furnace. Exhaust gas having low pressure/low flow of reduces the flow of the heated exhaust gas through the passageway of the inner member, thus reducing the electric output of the thermoelectric device.
As can be appreciated by those skilled in the art, it would be advantageous to provide a device for thermoelectric generation that can be heated by the exhaust of a furnace, e.g. but not limited to, the exhaust of a furnace for melting glass batch materials and does not have the limitations of the presently available devices.